Field The present invention pertains to the treatment of oil and sand cuttings, in particular sand-containing heavy oil and bitumen suspensions in water to release floatable bitumen components trapped or blocked by the sand matrix.

Background of the Invention

Drill cuttings are a pervasive waste product generated from developing oil wells. Instead of discharging drilling waste to the environment, oil -based mud cuttings can be treated in onsite settling ponds, or treated using thermal desorption technology, to reduce residual oil on cuttings sufficiently for disposal. Thermal desorption technology has been used widely in drilling cuttings processing, but the capital costs are high and there are treatability concerns with the recovered oil and its suitability for re-use. The problem is that the thermal energy required to distill enough

hydrocarbons from the cuttings to render them suitable for disposal may result in some cracking or other thermal degradation of the oil, creating aromatics and unsaturated hydrocarbons that adversely affect the toxicity and performance of the drilling fluid.

It is known that components in oil sands processing flowsheets, especially bitumen/water/sand/clay suspensions, are susceptible to undesirable gelation which creates "blocking gels" which act as a barrier to the flotation of entrained bitumen and heavy oil. This phenomenon is described by J.B. O'Carroll in University of Ottawa Masters Thesis "Factors Affecting Bitumen Recovery from Oil Sands" (1999).

Further discussion can be found in: Wallace, D., Komishke, B. and Wallwork, V., "On the Standardization of Extractability Protocols", Oil Sands 2006 Conference, Edmonton, Alberta, February 22 -24, 2006. A description of the effect of shear on the viscosity of suspensions of materials was also reported in Chow, R., Zhou, J., and Wallace, D., "The Rheology of Oil Sands Slurries", Oil Sands 2006 Conference, Edmonton, AB, February 22 - 24, 2006. In addition, an analysis of the bitumen recovery process from Syncrude Canada Ltd. states that the type of energy may be more important than the quantity of energy (i.e. shear may be the determining factor): Sanford, E.C., "Processability of Athabasca Oil Sand: Interrelationship Between Oil Sand Fine Solids, Process Aids, Mechanical Energy and Oil Sand Age After Mining," The Canadian Journal of Chemical Engineering, 1983, 61, 554 - 567. This analysis was done specifically in the context of initial slurrying - a step in the process that not only influences the initial liberation of bitumen from the oil sand but the interaction among particles that control subsequent flotation processes.

Accordingly, there is a recognized need for methods which can wholly or partially break up the oil-sand cuttings slurry in oil sands processing and in the collection of subsequent sand cuttings.

Sonic reactors (sometimes called sonic generators) that convert electrical energy into kinetic energy via acoustic resonance for transfer to process fluid mediums are known, e.g. Nyberg et al., US 5,005,773, incorporated herein by reference. They allow for maximum and efficient transmission of the kinetic energy emitted by the resonating element into the fluid medium, thus minimizing energy losses to the support structure. Industrial applications of sonic reactors include (a) grinding or dispersing of agglomerated minerals, and/or (b) concentrated mixing of solid, fluid and/or mixed solid-fluid mediums. The high intensity energy transferred to the fluid being processed facilitates deagglomeration of solids to allow for enhanced separation and recovery of desirable minerals, and/or uniformly distributes solid and/or fluid particles throughout the medium, which maximizes and intensifies the effective surface-to-surface contact shear area between fluid and/or solid mediums and allows for efficient conversion of desired chemical reactions and/or depositions. Summary of the Invention

According to one aspect of the invention, there is provided a method of treating oil and sand cuttings to reduce the oil content of the cuttings, comprising forming a slurry of the oil-sand cuttings and sonicating the slurry to release floatable entrained hydrocarbons.

According to another aspect of the invention, there is provided a method of wholly or partially rupturing and shearing bitumen flotation blocking gels of the bitumen- water- sands-clay suspensions during the processing of oil sands and cuttings by low frequency sonication. The oil-sand cuttings slurry is pumped through mixing chambers of a sonic reactor which are physically mounted to one or both free ends of the sonic reactor resonant element. Optionally, grinding media may be used in the mixing chambers. The acoustic frequency sonication breaks down and inhibits the formation of blocking gels and emulsions from the cuttings and related slurry mixtures, thereby releasing floatable entrained bitumen. The sonication may be carried out in an acoustic frequency range of approx. 20 Hz to 20,000 Hz, alternatively 50 to 500 Hz.

Further aspects of the invention and features of specific embodiments of the invention are described below.

Brief Description of the Drawings

Figure 1 is a schematic drawing of a portion of a sonic reactor apparatus for use in carrying out the method of the invention.

Figure 2 is a flow diagram of one embodiment of the treatment method of the invention.

Detailed Description

Drill cuttings comprising small sand particles are made into a slurry, i.e. and oil-sand cuttings slurry, or a water-oil-sand-clay cutting fluid slurry. Optionally, up to about 1,000 mg/kg of flocculants may be added to the slurry prior to sonication. The cutting fluid may include selected hydrocarbons, surfactants and polymers that optimize flow viscosity. Referring to Figure 1 , an apparatus that may be used to carry out the sonication is a sonic reactor having a mixing chamber 10 physically mounted to a free end of the sonic reactor resonant element 8. The sonic reactor may be of the type disclosed in Nyberg et al., US 5,005,773, or a multi-module prong-type acoustic frequency sonic reactor. The sonication accomplishes the shear effects required to facilitate enhanced rupturing and shearing of bitumen flotation blocking gels in the oil-sand cuttings slurry 14. Optionally, the mixing chamber holds grinding media 12, depending on the composition of the feed slurry. The grinding media are retained in the mixing chambers by a screen assembly 16.

Figure 2 depicts an embodiment of the method of the invention. In step 1 , cuttings from an oil well or a collection lagoon, with a significant quantity of wasted or spilled oil mixed with water, are stored in a largely unlined and uncovered condition, e.g. in tanks or bins. This comprises the oil-sand cuttings slurry that is subjected to the treatment of the invention.

In step 2, conventional gross material separation is done through an inclined screen for removal of bulk solids like large pieces of wood and rocks. This may alternatively be done in a water-sand-clay-bitumen separator tank.

In step 3, the slurry from step 2, which optionally may be heated, is subjected to low frequency sonication using an arrangement of multi-module horizontal bar-type sonic reactors comprised of one or more sonic reactor units. As described above, the sonic reactors are used to accomplish the shear effects required to facilitate enhanced rupturing and shearing of bitumen flotation blocking gels in a typical oil-sand cuttings slurry, e.g. a suspension of water-sand-clay-bitumen.

In step 4, primarily inorganic solids separation is performed on the sonicated slurry produced in step 3. It may utilize a screening configuration based on produced analytical data from the sonicated slurry. Alternatively, it may use an array of settling tanks. At this stage, the solids (sand) are substantially separated from the oil/water. The rejected solids are sufficiently clean to be returned to the land within local and federal regulations.

In step 5, the sonicated slurry left after the solids separation of step 4 is placed in a vessel designed to float bitumen. For example, a low velocity clarifier or membrane separation may be used to separate the oil and water fractions. This step 5 may include additional inorganic solids settling techniques. Recovered water and rejected separation solids are sent back to step 1 for further treatment. This may be a separate recovery collection cell and/or oily water storage (step 7) in which the water and rejected separation solids are contained before returning to step 1. The concentrated oil stream from step 5 is sent to step 6.

In step 6, the residual water is removed from the concentrated oil stream, leaving the recovered oil. Membrane separation as well as conventional energy-based separation may be employed in both evaporation and freeze crystallization unit operations.

Recovered water and rejected separation solids are sent to the recovery collection cell (step 7) and then to step 1 for further treatment.

Once separated from the residual water in step 6, the recovered oil product is reusable in industrial bulk oil applications. It has good flow viscosity and reduced sulfur content. It may be used in upgrading heavy oils and bitumen for higher value applications.

Example 1

Sonication of a bitumen-sand slurry was performed for intervals of approximately 2 to 180 seconds at a frequency in the range of about 100 Hz to 500 Hz. The heavy oil floated quickly and thoroughly and the remaining sand matrix demonstrated lower quantities of retained heavy oil. The results clearly show that acoustic frequency sonication is able to rupture the bitumen flotation blocking gels in the heavy oil or bitumen/sand/cutting fluid slurry and effectively separate the entrained heavy oil or bitumen from the remaining slurry. The runs summarized below were completed on field cuttings samples provided by one or more major industrial producers of oil sand field cuttings from Alberta, Canada. Optimization work was performed around the sonication performance which was based on qualitative observation prior to completing a quantitative analysis. This was a clear and reliable method of evaluation in that the produced sand was visually cleaner and lighter than the original sand cuttings samples, as shown by analytical data below in Tables 1 and 2.

Analyses were performed on the slurries before and after sonication and the results are shown in Table 1 :

Table 1

Units Pre Sonication Post Sonication

Mass Bitumen g 8.85 0.42

Mass % Bitumen wt % 9.64 0.36 (>96% reduction)

Mass % Solids wt % 90.42 99.71

Mass % Water wt % <0.01 < 0.01

Mass % Recovery wt % 100.07 100.07

Example 2

Sonication was performed as in Example 1 , but with the addition of a heating stage in which the oil sand cuttings slurry was heated to 30 to 90 degrees C. prior to sonication. Commercially this can be accomplished by heating the oil-sand cuttings slurry with a heat exchanger prior to step 3 of Figure 2. The sonicated slurry was analyzed and the results are shown in Table 2. The runs shown in Table 2 reflect variable oil concentrations in heated cutting samples and the overall success of separating oil from the cuttings samples with more than 99% separation efficiency. Table 2

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the following claims.